Infected aneurysms or pseudoaneurysms of the extracranial carotid artery are extremely rare, but they can lead to lethal complications. In some cases, infected pseudoaneurysms can be masked by the excessive inflammation of surrounding tissues. Here we describe the case of a 69-year-old woman with several comorbidities, who presented with a rapidly enlarging left neck bulge. CT was suggestive of an abscess involving the left common carotid artery. Colour Doppler ultrasound did not document intralesional flow. Abscess drainage under ultrasonographic assistance was attempted unsuccessfully, with collection of creamy, purple material. Surgical drainage of the abscess was, therefore, decided. As soon as necrotic tissue debridement was started, a massive haemorrhage originating from the common carotid artery invaded the surgical field. The carotid artery was then repaired with a bovine pericardial patch and covered with a pectoralis major muscle flap. The patient recovered without any neurological consequences. Revision of CT imaging revealed a very small misdiagnosed infected pseudoaneurysm. With better preoperative surgical planning and a good suspicion index, such a life-threatening emergency could have been avoided.